The use of hearing protective and noise attenuating devices is well known, and various types of devices are available including, but not limited to, ear muffs, semi-aural devices, and earplugs. Earplugs are often preferred for their effectiveness in attenuating sound and for comfort properties provided thereby.
An earplug generally comprises a sound attenuating element which is placed in the ear canal of a wearer to provide a desired sound attenuation. The sound attenuating element is commonly made of a resiliently compressible, full recovery material such as a foam or a rubber.
The earplug may further include a rigid or semi-rigid stem embedded partly or entirely in the resilient sound attenuating element. The stem provides a degree of rigidity to the earplug which enables the earplug to be easily inserted and pushed into the ear canal of a user. Further, where the stem extends from the sound attenuating element, it may serve as a handle of the earplug to facilitate insertion and removal of the earplug.
Commonly, resilient sound attenuating elements for earplugs are formed by molding techniques which utilize a specific mold to shape the sound attenuating element. For example, the resilient material in liquid form is injected into the mold and allowed to set therein. Once the material is solidified, the sound attenuating element is ejected from the mold.
If the earplug includes a stem, such is manufactured separately from the sound attenuating element. For example, the stem may be produced in a separate molding process. Once completed, the stem may be adhered adhesively to the sound attenuating element. Alternatively, the completed stem may be placed into the mold of the sound attenuating element when the resilient material is in the liquid form. In this way, the resilient material may cure around and bond onto the stem.
This multi-step molding and assembly procedure for forming stemmed foam earplugs is often inconvenient and cumbersome. For example, if a manufacturer desires several differently shaped and/or sized earplugs, he or she must produce and maintain an equivalently corresponding number of molds. Further, the material used to form the sound attenuating element may stick to the mold during the solidification process and thus tear or otherwise deform upon ejection. Also, sound attenuating elements cast in a mold as described may include seam lines from the mold and also necessarily include any imperfections on the molding surface of the mold. Further, the additional steps of manufacturing the stem and of affixing the stem to the sound attenuating element are often regarded as time consuming and costly.
Thus, a stemmed earplug is desired where the sound attenuating element and the stem may be produced conveniently, rapidly, and at reduced cost while still maintaining a high production quality.